I then cut a long rectangle that is 5 inches in height by 1 1/2 times the length of the front pieces. Fold over one of the long sides of the rectangle 1/2 inch and sew down. Then start shirring the back rectangle. If you haven't shirred something before, here is a great tutorial on shirring by Ruffles and Stuff.
Turn the garment right side out and press this seam down. Now turn it inside out again and press the bottom edge not attached to the gathered bottom and the sides under a 1/4 inch and sew these pieces down, making sure to capture the gathered edge under the turned edge so that the inside looks nice and neat..
Put the dress on and step back and enjoy your work, Here is my cutie enjoying her shirt again. Please feel free to link back to this post but please don't use my pictures without permission, especially those with my children in them. I know these steps may be hard to follow so if you have any questions, don't hesitate to ask.